The exhaust stream of a diesel engine is typically filtered using a diesel particulate filter (DPF). The DPF, which is positioned in the exhaust stream downstream of a catalyst, captures engine soot and other suspended particulate matter before it can be discharged via the tailpipe into the surrounding atmosphere. Soot production is heavily influenced by engine operation, for instance EGR valve position, turbo position, fuel injection timing, etc. Over time, soot loading accumulates in the porous media of the DPF. In-situ thermal regeneration of the DPF is therefore conducted periodically to burn off accumulated particulate matter.
DPF regeneration is typically performed by temporarily elevating the temperature of the exhaust stream passing through the DPF. A metered stream of fuel is injected into the exhaust stream. The exothermic reaction with a diesel oxidation catalyst (DOC) quickly raises exhaust temperatures to 600° C. or higher, thereby incinerating accumulated soot. Over time, substrate within the DPF may become cracked, melted, or pitted from repeated exposure to thermal stress and other factors. As a result, a DPF diagnostic is ordinarily performed in order to verify satisfactory performance of the DPF.